JP6090595B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine applied to a multi-cylinder internal combustion engine.

  Patent Document 1 describes an internal combustion engine that includes, for each cylinder, a first fuel injection valve that directly injects fuel into a cylinder and a second fuel injection valve that injects fuel into an intake passage. . In a control device applied to such an internal combustion engine, an imbalance diagnosis is performed to detect variation in the air-fuel ratio between cylinders.

  That is, first, the first imbalance diagnosis is performed at the time of engine operation only by fuel injection from the first fuel injection valve. After the first imbalance diagnosis is completed, the second imbalance diagnosis is performed during engine operation with fuel injection from both the first fuel injection valve and the second fuel injection valve. When it is detected by the second imbalance diagnosis that the air-fuel ratio varies between the cylinders, the third imbalance diagnosis is performed during engine operation with only fuel injection from the second fuel injection valve. . Thereby, it is possible to accurately detect abnormality of the first fuel injection valve and the second fuel injection valve.

JP 2014-31723 A

  Incidentally, some internal combustion engines are provided with an exhaust gas recirculation device that recirculates a part of the exhaust gas flowing in the exhaust passage into the intake passage. In such an internal combustion engine, exhaust gas may recirculate in the intake passage even when imbalance diagnosis is performed.

  An injection port for injecting fuel in the second fuel injection valve is located in the intake passage. Therefore, when the first imbalance diagnosis is performed, deposits derived from components contained in the exhaust gas recirculated into the intake passage adhere to the injection ports of the second fuel injection valves that are not performing fuel injection. May accumulate. Thus, when deposit accumulates in the injection opening of the 2nd fuel injection valve, the opening area of an injection opening will become narrow and it will become easy to reduce the amount of fuel injection from the 2nd fuel injection valve. Therefore, when fuel injection is performed from the second fuel injection valve, the actual fuel injection amount from the second fuel injection valve may be smaller than the target fuel injection amount.

  An object of the present invention is for an internal combustion engine capable of performing an imbalance diagnosis for detecting variation in air-fuel ratio among cylinders while suppressing deposit adhesion to a fuel injection valve that injects fuel into an intake passage. It is to provide a control device.

  An internal combustion engine controller for solving the above-described problems flows in a first fuel injection valve that injects fuel into a cylinder, a second fuel injection valve that injects fuel into an intake passage, and an exhaust passage. An apparatus that is applied to a multi-cylinder internal combustion engine that includes an exhaust gas recirculation device that recirculates a part of exhaust gas into an intake passage, and that performs an imbalance diagnosis for detecting variation in air-fuel ratio among cylinders. It is assumed. The internal combustion engine control device performs imbalance diagnosis during engine operation accompanied by fuel injection from the second fuel injection valve when performing imbalance diagnosis during engine operation by fuel injection from only the first fuel injection valve. A restriction process for restricting the recirculation of the exhaust gas into the intake passage by the exhaust gas recirculation device is performed more than once.

  When fuel is injected from the second fuel injection valve, even if the exhaust gas is recirculated into the intake passage, the deposit derived from the component contained in the exhaust gas injects fuel at the second fuel injection valve. Difficult to stick to mouth. On the other hand, when fuel is injected only from the first fuel injection valve, no fuel is injected from the second fuel injection valve, and therefore deposits derived from components contained in the exhaust gas flowing in the intake passage are first. It tends to adhere to the injection port of No. 2 fuel injection valve.

  According to the above configuration, when the imbalance diagnosis is performed during engine operation by fuel injection only from the first fuel injection valve, the imbalance diagnosis is performed during engine operation accompanied by fuel injection from the second fuel injection valve. Compared to the case, the exhaust gas is less likely to recirculate in the intake passage by the amount of restriction processing. As a result, even when the imbalance diagnosis is performed during engine operation by fuel injection from only the first fuel injection valve, the amount of exhaust gas recirculated into the intake passage itself is reduced. Deposits derived from components contained in the flowing exhaust gas are less likely to adhere to the injection port of the second fuel injection valve. That is, a decrease in the opening area of the injection port due to the deposit accumulation is suppressed, and a decrease in the fuel injection amount from the second fuel injection valve is less likely to occur. Therefore, it is possible to perform an imbalance diagnosis that detects variations in the air-fuel ratio among the cylinders while suppressing deposits on the fuel injection valve that injects fuel into the intake passage.

  For example, the limiting process is preferably a process for prohibiting exhaust gas recirculation into the intake passage by the exhaust gas recirculation device. According to this configuration, exhaust is not recirculated into the intake passage by performing the restriction process. Therefore, when performing an imbalance diagnosis during engine operation by fuel injection from only the first fuel injection valve, it is possible to suitably suppress deposit adhesion to the injection port of the second fuel injection valve.

  Further, the limiting process controls the exhaust gas recirculation device so that the amount of exhaust gas recirculated into the intake passage is smaller than when imbalance diagnosis is performed during engine operation involving fuel injection from the second fuel injection valve. It is good also as processing. Even in such a configuration, the amount of exhaust gas recirculated into the intake passage is reduced by performing the restriction process. Therefore, when imbalance diagnosis is performed during engine operation by fuel injection from only the first fuel injection valve, it is possible to suppress deposits from being deposited on the injection port of the second fuel injection valve.

The block diagram which shows the outline of a multicylinder internal combustion engine provided with the control apparatus which is one Embodiment of the control apparatus for internal combustion engines. The flowchart explaining the process sequence when the execution condition of imbalance diagnosis is materialized in the control apparatus of the embodiment. (A) is a timing chart showing changes in imbalance diagnosis, (b) is a timing chart showing changes in DI ratio, and (c) is a change in EGR opening correlated with the amount of exhaust gas recirculated into the intake passage. The timing chart which shows.

Hereinafter, an embodiment embodying a control device for an internal combustion engine applied to a multi-cylinder internal combustion engine will be described with reference to FIGS.
FIG. 1 shows a multi-cylinder internal combustion engine 10 including a control device 100 which is a control device for an internal combustion engine of the present embodiment. Although the internal combustion engine 10 has a plurality of cylinders, only one cylinder is illustrated in FIG.

  As shown in FIG. 1, a reciprocating piston 12 is accommodated in a cylinder 11 of the internal combustion engine 10. The reciprocating motion of the piston 12 is converted into a rotational motion by the connecting rod 13 and transmitted to the crankshaft 14. The rotational speed of the crankshaft 14 is detected by the crank position sensor 111.

  A combustion chamber 16 is defined by the inner peripheral surface of the cylinder 11, the top surface of the piston 12, and the cylinder head 15. An ignition plug 17 is provided at the upper part of the combustion chamber 16 so as to face the piston 12. The cylinder 11 is provided with a first fuel injection valve 18 that directly injects fuel into the cylinder 11, that is, into the combustion chamber 16.

The combustion chamber 16 is connected to an intake passage 20 for guiding intake air to the combustion chamber 16 and an exhaust passage 30 through which exhaust gas discharged from the combustion chamber 16 flows.
The intake passage 20 is provided with a throttle valve 21 that adjusts the intake air amount that is the amount of intake air introduced into the combustion chamber 16. The throttle valve 21 is driven by a motor 22. A second fuel injection valve 23 that injects fuel into the intake passage 20 is provided in the intake passage 20 on the downstream side of the intake side of the throttle valve 21. An injection port 23 a for injecting fuel in the second fuel injection valve 23 is located in the intake passage 20. Further, an air flow meter 112 that detects the amount of intake air is provided in the intake passage 20 on the intake upstream side of the throttle valve 21.

  The exhaust passage 30 is provided with an air-fuel ratio sensor 113 that detects the oxygen concentration of the exhaust flowing through the exhaust passage 30. Based on the oxygen concentration of the exhaust gas detected by the air-fuel ratio sensor 113, the air-fuel ratio of the air-fuel mixture combusted in the combustion chamber 16 can be estimated.

  Further, the internal combustion engine 10 is provided with an exhaust gas recirculation device 40 that recirculates a part of the exhaust gas flowing through the exhaust passage 30 into the intake passage 20. The exhaust gas recirculation device 40 includes a recirculation passage 41 having one end connected to the exhaust passage 30 and the other end connected to the intake passage 20. The recirculation passage 41 is connected to the intake passage 20 on the intake upstream side of the second fuel injection valve 23. An adjustment valve 42 for adjusting the recirculation amount of the exhaust gas into the intake passage 20 is provided at a connection portion of the recirculation passage 41 with the intake passage 20. In addition, a cooling device 43 for cooling high-temperature exhaust gas flowing in the reflux passage 41 is provided in the reflux passage 41 closer to the exhaust passage 30 than the adjustment valve 42.

  In addition to the crank position sensor 111, the air flow meter 112, and the air-fuel ratio sensor 113, a throttle opening sensor 114, an accelerator opening sensor 115, and the like are electrically connected to the control device 100 that controls the internal combustion engine 10. The throttle opening sensor 114 detects the opening of the throttle valve 21. The accelerator opening sensor 115 detects an accelerator opening that is an operation amount of the accelerator pedal 50 by the driver of the vehicle. And the control apparatus 100 implements various controls, such as fuel injection control, based on the information detected by such various detection systems.

  For example, the control device 100 determines the DI ratio according to the operating state of the internal combustion engine 10. The DI ratio is the fuel from the first fuel injection valve 18 with respect to the total fuel injection amount that is the sum of the fuel injection amount from the first fuel injection valve 18 and the fuel injection amount from the second fuel injection valve 23. This is the ratio of the injection amount. When the DI ratio is “1”, the control device 100 does not inject fuel from the second fuel injection valve 23 but injects fuel only from the first fuel injection valve 18. Further, when the DI ratio is “0 (zero)”, the control device 100 does not inject fuel from the first fuel injection valve 18 but injects fuel only from the second fuel injection valve 23. Further, when the DI ratio is “α (α is a value larger than 0 and smaller than 1)”, the control device 100 supplies fuel from both the first fuel injection valve 18 and the second fuel injection valve 23. To spray.

  Further, in the control device 100 of the present embodiment, an imbalance diagnosis for detecting a variation in air-fuel ratio between cylinders is performed for each fuel injection mode. Specifically, the control device 100 performs an imbalance diagnosis when the DI ratio is “1”, that is, when the engine is operated by fuel injection from only the first fuel injection valve 18. The control device 100 also performs imbalance diagnosis even when the DI ratio is “α”, that is, during engine operation by fuel injection from both the first fuel injection valve 18 and the second fuel injection valve 23. To do. Further, the control device 100 performs the imbalance diagnosis even when the DI ratio is “0 (zero)”, that is, during engine operation by fuel injection from only the second fuel injection valve 23. The engine operation when the DI ratio is smaller than “1” corresponds to “engine operation with fuel injection from the second fuel injection valve 23”.

  Here, an example of imbalance diagnosis will be described. One of the factors that cause the air-fuel ratio to vary between the cylinders is a variation in the fuel injection amount between the cylinders. For example, assume that one of a plurality of cylinders is a specific cylinder, and the fuel injection amount for the specific cylinder is larger than the fuel injection amounts for other cylinders other than the specific cylinder. In this case, the rotation speed of the crankshaft 14 is faster during the combustion process in the specific cylinder than in the combustion process in the other cylinders. That is, the rotation speed of the crankshaft 14 varies within one cycle of the internal combustion engine 10.

  Therefore, during the imbalance diagnosis, the variation in the rotational speed of the crankshaft 14 in one cycle of the internal combustion engine 10 is observed. When the difference between the maximum value and minimum value of the rotation speed in one cycle is equal to or greater than a predetermined threshold value, it is diagnosed that the air-fuel ratio may vary between the cylinders, while the difference is less than the threshold value. Sometimes, it can be diagnosed that the air-fuel ratio does not vary between cylinders. Such a diagnosis is performed for a predetermined period. For example, when a cycle in which the difference is equal to or greater than the threshold value continues for a plurality of times within a certain period, it can be diagnosed that the air-fuel ratio varies between the cylinders.

  Incidentally, a technique for detecting the degree of variation in the air-fuel ratio between cylinders is already known. For example, in addition to the method for observing the variation in the rotational speed of the crankshaft 14, a method for observing the variation in the oxygen concentration detected by the air-fuel ratio sensor 113, that is, the variation in the air-fuel ratio calculated based on the oxygen concentration, is also known. ing.

  When exhaust gas is recirculated into the intake passage 20 by the exhaust gas recirculation device 40 and the imbalance diagnosis is performed in a state where the DI ratio is “1”, no fuel is injected from the second fuel injection valve 23. Therefore, deposits derived from components contained in the exhaust gas recirculated into the intake passage 20 may adhere to the injection port 23a of the second fuel injection valve 23 located in the intake passage 20. Therefore, in the present embodiment, when performing an imbalance diagnosis during engine operation by fuel injection from only the first fuel injection valve 18, the imbalance diagnosis is performed during engine operation accompanied by fuel injection from the second fuel injection valve 23. The restriction process for restricting the recirculation of the exhaust gas into the intake passage 20 by the exhaust gas recirculation device 40 is performed more than when it is performed. Specifically, when an imbalance diagnosis is performed during engine operation by fuel injection from only the first fuel injection valve 18, exhaust gas recirculation into the intake passage 20 by the exhaust gas recirculation device 40 is prohibited by performing restriction processing. Like to do.

  On the other hand, when the imbalance diagnosis is performed when the DI ratio is not “1”, since the fuel is injected from the second fuel injection valve 23, the exhaust gas is recirculated into the intake passage 20. Therefore, deposits derived from components contained in the exhaust gas are unlikely to adhere to the injection port 23a of the second fuel injection valve 23. Therefore, when imbalance diagnosis is performed during engine operation accompanied by fuel injection from the second fuel injection valve 23, the exhaust gas recirculation device 40 is configured to recirculate exhaust gas into the intake passage 20 without performing restriction processing. .

Next, a processing procedure executed by the control device 100 when the imbalance diagnosis execution condition is satisfied will be described with reference to the flowchart shown in FIG.
As shown in FIG. 2, in this process, the control device 100 determines whether or not the current DI ratio is “1” (step S11). That is, in step S11, it is determined whether or not the current engine operation is an engine operation by fuel injection from only the first fuel injection valve 18 for in-cylinder injection. If the DI ratio is “1” (step S11: YES), the control device 100 starts a limiting process (step S12). In this case, the control device 100 prohibits the recirculation of the exhaust gas into the intake passage 20 by closing the adjustment valve 42 of the exhaust gas recirculation device 40. Thereafter, the control device 100 shifts the process to the next step S13.

  On the other hand, when the DI ratio is not “1” (step S11: NO), the control device 100 shifts the process to the next step S13 without performing the restriction process (step S12).

  In step S13, the control device 100 performs an imbalance diagnosis. And the control apparatus 100 determines whether the elapsed time after the imbalance diagnosis was started has reached the predetermined implementation period (step S14). This implementation period is the time required for imbalance diagnosis. When the elapsed time since the start of the imbalance diagnosis has not yet reached the implementation period (step S14: NO), the control device 100 continues the imbalance diagnosis (step S13). On the other hand, when the elapsed time from the start of the imbalance diagnosis reaches the implementation period (step S14: YES), the control device 100 ends the imbalance diagnosis. Then, the control device 100 determines whether or not the restriction process is being performed (step S15). When the restriction process is being performed (step S15: YES), the control device 100 ends the restriction process (step S16), and then ends the process. On the other hand, when the restriction process is not being performed (step S15: NO), the control device 100 ends the process without performing step S16.

Next, the operation at the time of imbalance diagnosis will be described with reference to the timing chart shown in FIG.
As shown in FIGS. 3A, 3 </ b> B, and 3 </ b> C, when the imbalance diagnosis execution condition is satisfied at the first timing t <b> 1 where the DI ratio is “1”, The EGR opening that is the opening of the adjustment valve 42 of the recirculation device 40 becomes “0%”, and the recirculation of the exhaust gas into the intake passage 20 is prohibited. That is, the recirculation amount of the exhaust gas into the intake passage 20 is smaller than that immediately before the start of the imbalance diagnosis. Then, during engine operation by fuel injection only from the first fuel injection valve 18, the imbalance diagnosis is performed in a state where the recirculation of the exhaust gas into the intake passage 20 is prohibited in this way. When the imbalance diagnosis is ended at the second timing t2 thereafter, the restriction process is also ended. That is, the prohibition of exhaust gas recirculation into the intake passage 20 is released, and the exhaust gas is recirculated into the intake passage 20. For example, at the second timing t2, the EGR opening is returned to the opening just before the start of the imbalance diagnosis. At this time, if the prohibition of the recirculation of the exhaust gas into the intake passage 20 is canceled, the EGR opening need not be returned to the opening just before the start of the imbalance diagnosis.

  On the other hand, when the imbalance diagnosis execution condition is satisfied at the third timing t3 when the DI ratio is “α (0 <α <1)” and the imbalance diagnosis is performed, the DI ratio is “1”. In contrast, the recirculation of the exhaust gas into the intake passage 20 is not limited. That is, during engine operation by fuel injection from both the first fuel injection valve 18 and the second fuel injection valve 23, the imbalance diagnosis is performed in a state where exhaust gas is recirculated in the intake passage 20. Then, such an imbalance diagnosis is terminated at the subsequent fourth timing t4.

  Similarly, when the imbalance diagnosis execution condition is satisfied at the fifth timing t5 when the DI ratio is “0 (zero)” and the imbalance diagnosis is performed, the recirculation of the exhaust gas into the intake passage 20 is limited. Not. That is, the imbalance diagnosis is performed in a state where the exhaust gas is recirculated in the intake passage 20 even when the engine is operated by fuel injection from only the second fuel injection valve 23. Then, such an imbalance diagnosis is terminated at a subsequent sixth timing t6.

As mentioned above, according to the said structure and effect | action, the effect shown below can be acquired.
(1) When imbalance diagnosis is performed during engine operation with fuel injection from only the first fuel injection valve 18, when imbalance diagnosis is performed during engine operation with fuel injection from the second fuel injection valve 23 Unlike the above, a restriction process is performed. As a result, even when imbalance diagnosis is performed during engine operation by fuel injection from only the first fuel injection valve 18, deposits derived from components contained in the exhaust are injected into the injection port of the second fuel injection valve 23. It becomes difficult to adhere to 23a. As a result, a decrease in the opening area of the injection port 23a due to deposits adhering to the injection port 23a is suppressed, and the shortage of the fuel injection amount from the second fuel injection valve 23, that is, the target fuel injection amount and the actual The difference from the fuel injection amount is less likely to occur. Therefore, the imbalance diagnosis can be performed while suppressing the adhesion of deposits to the second fuel injection valve 23.

  (2) In the present embodiment, exhaust is not recirculated into the intake passage 20 by performing the restriction process. Therefore, even when the imbalance diagnosis is performed during engine operation by fuel injection from only the first fuel injection valve 18, the injection port 23a of the second fuel injection valve 23 of the deposit derived from the components contained in the exhaust gas. Adhesion to can be suitably suppressed.

  (3) On the other hand, when imbalance diagnosis is performed during engine operation accompanied by fuel injection from the second fuel injection valve 23, exhaust gas is recirculated into the intake passage 20 because restriction processing is not performed. Therefore, a period in which the recirculation of exhaust gas into the intake passage 20 is restricted even when imbalance diagnosis is performed during engine operation accompanied by fuel injection from the second fuel injection valve 23 as compared with the case where the restriction process is performed. Therefore, the fuel consumption efficiency of the internal combustion engine 10 can be increased.

The above embodiment may be changed to another embodiment as described below.
If the restriction process can make the EGR opening degree correlated with the recirculation amount of the exhaust gas into the intake passage 20 smaller than when the imbalance diagnosis is performed in a situation where the DI ratio is not “1”. The EGR opening may be set to a value larger than “0 (zero)%”. Even in this case, by performing the restriction process when the imbalance diagnosis is performed under the situation where the DI ratio is “1”, the recirculation amount of the exhaust gas into the intake passage 20 is changed to the DI ratio “1”. This can be reduced compared to when the imbalance diagnosis is performed under circumstances that are not. As a result, it is possible to suppress the deposit derived from the components contained in the exhaust from adhering to the injection port 23a of the second fuel injection valve 23.

  When the condition for performing imbalance diagnosis is satisfied under the condition where the DI ratio is “1”, the imbalance diagnosis is performed after a predetermined time has elapsed since the recirculation of the exhaust gas into the intake passage 20 is prohibited by the restriction process. May be started. In this way, by delaying the start of the imbalance diagnosis from the start of the limiting process, it is possible to further enhance the effect of suppressing the deposit derived from the exhaust from adhering to the injection port 23a of the second fuel injection valve 23.

  Even when the imbalance diagnosis is performed under a situation where the DI ratio is not “1”, the EGR opening may be made smaller than that immediately before the start of the imbalance diagnosis. However, in this case, it is preferable that the limit value of the EGR opening when the DI ratio is not “1” is larger than that when the DI ratio is “1”. As a result, the recirculation amount of exhaust gas into the intake passage 20 when the imbalance diagnosis is performed under the condition where the DI ratio is “1”, and the imbalance diagnosis is performed under the condition where the DI ratio is not “1”. The amount of exhaust gas recirculated into the intake passage 20 can be reduced.

  As a method for recirculating the exhaust gas to the combustion chamber 16 in the cylinder 11, the exhaust valve is opened during the intake process in addition to a method of recirculating the exhaust gas into the intake passage 20 via the exhaust gas recirculation device 40. Also known is a method of causing the exhaust gas in the exhaust passage 30 to flow backward to the combustion chamber 16 by adjusting the opening timing of the exhaust valve. Even with this method, part of the exhaust gas that has flowed back from the exhaust passage 30 into the combustion chamber 16 may flow into the intake passage 20. Therefore, as a limiting process in the case of using the method of causing the exhaust gas in the exhaust passage 30 to flow backward to the combustion chamber 16 as described above, for example, by adjusting the opening timing of the exhaust valve, the exhaust gas is discharged from the exhaust passage 30 during the intake process. It is preferable to carry out a process of reducing the amount of backflow to the combustion chamber 16 or a process of maintaining the exhaust valve closed during the intake process.

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 11 ... Cylinder, 18 ... 1st fuel injection valve, 20 ... Intake passage, 23 ... 2nd fuel injection valve, 30 ... Exhaust passage, 40 ... Exhaust gas recirculation apparatus, 100 ... Control apparatus for internal combustion engines The control apparatus which is an example.

Claims (3)

A first fuel injection valve that injects fuel into the cylinder, a second fuel injection valve that injects fuel into the intake passage, and an exhaust gas recirculation that recirculates part of the exhaust gas flowing through the exhaust passage into the intake passage. And a multi-cylinder internal combustion engine comprising:
A control device for an internal combustion engine that performs an imbalance diagnosis for detecting a variation in air-fuel ratio between cylinders,
When the imbalance diagnosis is performed during engine operation by fuel injection from only the first fuel injection valve, the imbalance diagnosis is performed more than when the imbalance diagnosis is performed during engine operation accompanied by fuel injection from the second fuel injection valve. A control device for an internal combustion engine, wherein a restriction process for restricting the recirculation of exhaust gas into the intake passage by the exhaust gas recirculation device is performed. The control device for an internal combustion engine according to claim 1, wherein the restriction process is a process for prohibiting recirculation of exhaust gas into the intake passage by the exhaust gas recirculation device. In the limiting process, the exhaust gas recirculation amount is controlled by controlling the exhaust gas recirculation device, so that the imbalance diagnosis is performed during engine operation involving fuel injection from the second fuel injection valve. The control device for an internal combustion engine according to claim 1, wherein the processing is a process of reducing the amount of the internal combustion engine.